Minimally invasive spinal fusion system and method

ABSTRACT

Disclosed herein are minimally invasive systems and method for stabilizing the spine, while preserving a degree of spinal flexion and extension of the spine at the level of the stabilized vertebrae postoperatively. The systems and methods can include an expandable anchor and rod that span an intervertebral disc. The anchor can have interstices, and ends in two adjacent vertebral bodies. The system can also include a volume of bone cement media.

PRIORITY CLAIM

This application claims the benefit under 35 U.S.C. §120 as acontinuation application of U.S. patent application Ser. No. 14/559,071filed on Dec. 3, 2014, which in turn claims the benefit of 35 U.S.C.§119(e) as a nonprovisional application of U.S. Prov. App. No.62/039,863 filed on Aug. 20, 2014. Each of the foregoing priorityapplications are hereby incorporated by reference in their entireties.

BACKGROUND

Most spinal fusions are performed for patients with back pain with orwithout radicular symptoms (radiating pain) or neurogenic claudication(pain with walking) caused by degenerative disc disease (spondylosis).Roughly 90% of all spine surgeries involve fusion. Over 465,000 spinalfusions were performed in 2011 in the US at a cost of nearly 13 billiondollars.

Not to be limited by theory, pain from such pathology is believed to becaused by abnormal motion (instability). Fusion is performed to reduceor eliminate the motion of the degenerated disc segment by immobilizingthe adjacent vertebral bodies. The majority of spinal fusions areperformed with a posterolateral approach with bone graft material placedacross the facets, lamina and transverse processes. A combination oftranspedicular screws and connecting rods or plates provideimmobilization of the vertebra until the bone graft material can form asolid bony fusion mass. A growing number of fusions are performed withan anterior approach with the bone graft placed in the disc space toallow bony fusion of the vertebral bodies across the disc space.Anterior fusions are typically performed in conjunction withposterolateral fusion rods to provide the immobilization needed for thebony fusion across the disc to occur. Bony fusion may take 6-12 monthsand fusion failure rates of 10-40% are reported in the literature.

SUMMARY

Disclosed herein are minimally invasive systems and methods forstabilizing a spine. In some embodiments, a method for stabilizing thespine includes one or more of the following steps: creating a pedicularaccess channel in a pedicle to access the interior of a first vertebralbody; inserting an introducer cannula into the pedicle; inserting ahollow needle through a central lumen of the introducer cannula into theinterior of the first vertebral body, through an intervertebral disc,and into the interior of a second vertebral body adjacent the firstvertebral body; inserting an anchor through a central lumen of thehollow needle such that a distal end of the anchor is within theinterior of the second vertebral body, a proximal end of the anchor iswithin the interior of the first vertebral body, and a central portionof the anchor spans the intervertebral disc; expanding the distal end ofthe anchor within the interior of the second vertebral body; expandingthe proximal end of the anchor within the interior of the firstvertebral body; flowing a first volume of bone cement media into thedistal end of the anchor within the interior of the second vertebralbody; flowing a second volume of bone cement media into the proximal endof the anchor within the interior of the first vertebral body; insertinga flexible rod through the central lumen of the hollow needle, such thata distal portion of the flexible rod is positioned within the interiorof the second vertebral body and in contact with the first volume ofbone cement media, the proximal portion of the flexible rod ispositioned within the interior of the first vertebral body, and acentral portion of the rod spans the intervertebral disc, wherein theflexible rod resides at least partially within an interior of theanchor. In some embodiments, substantially no bone cement media flowswithin the intervertebral disc. In some embodiments, the method does notinvolve a discectomy procedure. The bone cement media can include PMMA,for example, such as between about 1 cc and 5 cc, or about 2 cc andabout 3 cc. The flexible rod can comprise a carbon fiber material, suchas PEEK. Expanding the distal end of the anchor within the interior ofthe second vertebral body and expanding the proximal end of the anchorwithin the interior of the first vertebral body can comprise expanding aballoon. In some embodiments, inserting the anchor step comprisesinserting the anchor carried proximate the distal end of a ballooncatheter. In some embodiments, a central portion of the anchor is notexpanded, and the distal and proximal expanded portions of the anchorhave a maximal expanded diameter that is at least 1.5×, 2×, 3×, or moreof the unexpanded diameter of the central portion of the anchor. Theanchor can comprise a shape memory material, such as Nitinol. The anchorcan be inserted in a compressed, substantially tubular configuration.The introducer cannula can have a diameter of, for example, betweenabout 8 Gauge to about 12 Gauge. Following insertion of the flexible rodthe first and second volumes of bone cement media harden, fixing theanchor and flexible rod in place. In some embodiments, flowing thesecond volume occurs after the inserting a flexible rod step, such thatthe proximal end of the flexible rod is in contact with the secondvolume of bone cement media after the flowing the second volume step.

Also disclosed herein is a system for stabilizing the spine. The systemcan include, for example: an anchor having a proximal end, a distal end,and a central portion, the anchor having a compressed tubularconfiguration and an expanded configuration wherein the proximal end andthe distal end of the anchor are expanded while the central portion ofthe anchor is not expanded, wherein the proximal end and the distal endof the anchor have maximal expanded diameters at their widest portionsof at least about 2× the diameter of the central portion of the anchor,wherein the anchor is sized and configured such that the proximal end ofthe anchor can reside within the interior of a first vertebrae, thedistal end of the anchor can reside within the interior of a secondvertebrae adjacent the first vertebrae, and the central portion of theanchor spans an intervertebral disc between the first vertebrae and thesecond vertebrae, wherein the anchor is defined by a shape memory frameand interstices within the frame; and a flexible carbon fiber roddimensioned to fit within an interior of the anchor, such that whenimplanted the flexible rod is configured to reside substantially withinthe anchor, wherein the distal end of the flexible rod is configured toreside within the distal end of the anchor within the interior of thesecond vertebrae, the proximal end of the flexible rod is configured toreside within the proximal end of the anchor within the interior of thefirst vertebrae and the central portion of the anchor is configured tospan an intervertebral disc between the first vertebrae and the secondvertebrae. The flexible carbon fiber rod comprises PEEK in some cases.When implanted, the flexible carbon fiber rod is configured to allow forat least 15 degrees, 30 degrees, or more of flexion of a patient'sspine. In some embodiments, the system also includes a balloon cathetercomprising a balloon configured to expand the proximal end and thedistal end of the anchor. The anchor can be carried on a distal end ofthe balloon catheter. The system can also include a volume of bonecement media, such as PMMA. The system can also include an introducercannula comprising a central lumen and a stylet configured to reside atleast partially within the central lumen of the introducer cannula. Thesystem can also include a curvable hollow needle comprising a centrallumen configured to reside at least partially within the central lumenof the introducer cannula. The system can also include an injectorneedle in some embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an access cannula that can be part of a spinalstabilization system, in some embodiments.

FIG. 1B illustrates a hollow curvable needle that can be part of aspinal stabilization system, in some embodiments.

FIG. 1C illustrates an anchor carried by a balloon catheter that can bepart of a spinal stabilization system, in some embodiments.

FIG. 1D illustrates a balloon catheter that can be part of a spinalstabilization system, in some embodiments.

FIG. 1E illustrates a curvable media injector that can be part of aspinal stabilization system, in some embodiments.

FIG. 1F illustrates a flexible carbon fiber rod that can be part of aspinal stabilization system, in some embodiments.

FIGS. 2A-2I illustrate various steps of a method of stabilizing a spine,according to some embodiments.

DETAILED DESCRIPTION

Because of the high morbidity and high cost of the current methods ofspinal fusion, an effective, less invasive spinal fusion at lower costwould be a significant improvement. The proposed method of spinal fusioncould be done percutaneously as an outpatient rather than as an opensurgical procedure which typically requires a several day inpatientstay.

Systems and methods disclosed herein can, in some embodiments, involvecurrently available materials approved by the FDA for human use, as wellas materials that could be approved at a later date. The implantedmaterial can include, for example, one, two, or more sources of media,including bone cement material such as PMMA (polymethylmethacrylate), ashape memory material such as the superelastic memory alloy nitinol(nickel titanium), and a polymer, including carbon reinforced PEEK(polyether ether ketone), and/or organic thermoplastic polymer. PMMA isextremely resistant to compressive stress. PMMA bone cement can be madefrom methylmethacrylate, polymethylmethacrylate, esters of methacrylicacid, or copolymers containing polymethylmethacrylate and polystyrene.Carbon fiber reinforced polymers such as PEEK are extremely resistant tobending stress. Nitinol (nickel titanium alloy) is a shape memory alloyresistant to repetitive bending stress.

Candidates for conventional spinal fusion can benefit from the systemsand methods disclosed herein. The fusion can involve cervical, thoracic,lumbar, and/or sacral vertebrae in some embodiments. In someembodiments, a subgroup of patients who may especially benefit are olderpatients with osteoporosis who are poor surgical candidates and have fewoptions for treatment.

Systems and methods for spinal fusion or stabilization are describedherein. Various non-limiting embodiments of elements that can be usedwithin systems and methods herein are illustrated in FIGS. 1A-1F. Thesystem can include, in some embodiments, an access cannula 10 having aproximal end 16, a handle 14, and a distal end 18 with a central lumen12 (shown in FIG. 1A) with at least one input port and exit port. Thecentral lumen 12 of the access cannula 10 can house an inner stylet (notshown) therethrough. The system can also include a curvable needle 20having a distal end 24, with a central lumen 22 (shown in FIG. 1B)configured to fit within the central lumen 12 of the access cannula 10,and a perforated anchor 30 having a central lumen, a first end, a secondend, and an elongate section between the first and the second end. Theaccess cannula 10 and/or the curvable needle 12 can have indicia alongits length which can be radiopaque markers in some embodiments.

The anchor 30 is shown in FIG. 1C in a radially compressed, generallytubular configuration, and can be sized and configured to be placedwithin the central lumen 12 of the access cannula 10 for delivery intothe spine, and mounted over the distal end of a high-pressure ballooncatheter 41 or other expandable member in some embodiments. The anchor30 can include perforations or cells sized and configured to allow forthe passage of liquid bone cement therethrough, while allowingpreventing passage of bone cement after hardening (e.g., solid cement)which remains confined within the anchor 30. The perforations or cellscan be laser cut or otherwise created within the anchor 30. The firstend 32 and the second end 34 of the anchor 30 can each include one ormore discrete radially and/or axially expandable sections, such as aself-expandable or balloon-expandable section. In some embodiments, theexpandable first end 32 and second end 34 can be expanded in diameter toabout or at least about 1.25×, 1.5×, 1.75×, 2×, 3×, 4×, 5×, 6×, 7×, 8×,9×, 10×, or more relative to the unexpanded diameter of the anchor 30.In some embodiments, the central elongate section 36 of the anchor isnon-expandable or expandable/expanded to a lesser degree than the endsections 32, 34. The anchor 30 can be made of, for example, a metal ormetallic alloy, such as a shape memory material such as nitinol orElgiloy for example, stainless steel, and/or a polymer (includingbiodegradable polymers) or other materials in other embodiments. Theanchor 30 can be sized and configured such that the first end 32 iscontained within the cancellous bone of a first vertebrae, the secondend 34 is contained within the cancellous bone of a second vertebraeadjacent the first vertebrae (either in a cephalad or caudal direction),and the elongate section 36 spans an intervertebral disc between thefirst and second vertebrae.

As illustrated in FIG. 1D, the system can also include one, two, or moreexpandable members such as a balloon 40 on or proximate the distal endof balloon catheter 41 and configured to radially expand the anchor. Insome embodiments the expandable member has sufficient strength to createa cavity within the cancellous bone as well. In some embodiments, theballoon 40 can be inflated to an inflation pressure of about or at leastabout 15 atm, 20 atm, 25 atm, 30 atm, or more.

The system can also include a cement injection needle 50 which can havea distal steerable and/or curvable portion in some embodiments asillustrated in FIG. 1E. The injection needle 50 (as well as curvableneedle 20) can have a bent or curved unstressed state (e.g., made of ashape memory material) that is substantially straight while housedwithin a tube/sheath having sufficient column strength, but assumes itsunstressed state upon advancing out of, or withdrawal of thetube/sheath. In some embodiments, the needle 50 is steerable andcurvable by, for example, the use of one, two, or more pullwiresoperably connected to the distal end of the needle 50 and operablyconnected proximally to an adjustment control, such as a wheel, dial, orother element that can be adjusted by the physician to adjust thetension on the pullwire(s) and thus adjust the degree of curvature ofthe distal end of the needle 50, such as through a working range. Theneedle 50 can include one, two, or more distally facing and/or laterallyfacing exit ports for delivery of the cement or other media to alocation within the cancellous bone.

As illustrated in FIG. 1F, the system can also include one, two, or moreflexible rods 60 with first end 62 and second end 64, such as carbonfiber rods configured to be at least partially or completely housedwithin the central lumen of the anchor. In some embodiments the rods 60are sufficiently flexible to not substantially hinder flexion orextension of the spine when implanted into a patient. As noted above,the rods may be made of PEEK, carbon fiber PEEK, polyetherketoneketone(PEKK), polysulfone, polyetherimide, polyimide, ultra-high molecularweight polyethylene (UHMWPE), cross-linked UHMWPE, nano-materialreinforced polymers, another medical grade polymer material, or a hybridmetal-polymer rod in some embodiments. In some embodiments, the rods aresized and configured to span no more than a single intervertebral disc(although the rods could be sized and configured to span multiple discsin other embodiments), and can be from about 1 mm to about 3 mm indiameter in some cases, such as about 2 mm in diameter.

The spinal stabilization system can also include one, two, or morevolumes of media for injection into the cancellous bone. The media couldinclude, for example, one, two, or more bone cement materials such asPMMA, for injecting into the first and second end of the anchor tostabilize the anchor within adjacent vertebrae. In some embodiments themedia could be injected in a liquid or gel-like state that hardens orotherwise solidifies some time after injection into the vertebralcavity. The media could also include, for example, bone growth material,stem cells, and/or one, two, or more other therapeutic agents, such as agrowth factor, anesthetic agent, steroid or other anti-inflammatoryagent, narcotic or non-narcotic pain control agent, an antibiotic, anantibody, an anti-cancer chemotherapeutic agent, radiation-emittingmaterials, and the like.

FIGS. 2A-2I illustrate a method of performing a minimally invasive(e.g., percutaneous) spinal fusion procedure, according to someembodiments of the invention. Access to the first vertebra V1 can bewith an unipedicular or bipedicular approach with an access cannula 10,such as a straight cannula about 8, 9, 10, 11, 12, or other gauge indimension, as illustrated in FIG. 2A. The cannula 10 can be advanced tojust beyond the pedicle P into the posterior vertebral body and theinner stylet is then removed.

Through the cannula 10, a needle 20, such as a shape memory nitinolneedle with a curved unstressed state, such as about 12 gauge indimension (or 1, 2, 3, 4, or more gauge smaller than the diameter of thecentral lumen 12 of the cannula 10 in some cases), would be advanced andthe distal end curved in a cephalad direction as shown (or a caudaldirection in other embodiments) to cross the intervertebral disc space Dinto the anterior inferior aspect of the adjacent vertebral body V2, asillustrated in FIG. 2B.

The inner stylet of the nitinol needle 20 can be removed and astent-like perforated anchor 30, which can be a metal or metal alloysuch as a nitinol anchor mounted on a high pressure balloon can bepassed through the needle 20 to span the intervertebral disc space D, asillustrated in FIG. 2C. The balloon catheter 41 can be deployed, and thedistal end 32 of the anchor 30 in the superior vertebral body V2 can bedilated with the balloon 40 (not shown for clarity) to open up theanchor's interstices (cells), as shown in FIG. 2D. The balloon 40 can bewithdrawn into the inferior vertebral body V1 and the proximal portion34 dilated, as shown in FIG. 2F.

The balloon catheter 41 can be removed and a curvable and/or steerablehollow injection needle 50, such as a nitinol needle having an about 14gauge dimension in some embodiments can be advanced into the distal end32 of the anchor 30. In some embodiments, the balloon catheter 41 neednot be withdrawn immediately after creating a cavity in either thesuperior vertebral body V2 or the inferior vertebral body V1 (but can bedeflated in some embodiments), and the injection needle 50 can passthrough a lumen of the balloon catheter 41, or be integral with theballoon catheter 41 in some embodiments. An appropriate amount of media90, such as bone cement or other stabilizing material, such as betweenabout 1-5 cc or 2-3 cc, or about 1 cc, 1.5 cc, 2 cc, 2.5 cc, 3 cc, 3.5cc, 4 cc, 4.5 cc, or 5 cc of PMMA bone cement in some embodiments, canbe injected into the distal 32 portion of the anchor 30 under imaging,such as constant fluoroscopic visualization as the cement flows throughthe interstices of the anchor 30 and into the normal bone marrow spaceand bony trabeculae, as shown in FIG. 2E. This will stabilize the anchor30 in place and maximize the surface area contact of cement 90 and boneas the media cures. In some embodiments, the bone cement 90 is injectedinto cavities within the vertebrae only, and no bone cement 90 orsubstantially no bone cement 90 resides or migrates into theintervertebral disc space D, either within or outside the centralelongate portion 36 of the anchor 30 which is not radially expanded insome embodiments. This can be advantageous in some cases, such thathardened bone cement 90 or other material is not present in theintervertebral disc space D allowing for maintenance of some degree ofspinal flexion, extension, and rotation postoperatively. In someembodiments, partial or complete discectomies are not required to beperformed during the procedure, to better maintain the intervertebraldisc D as mentioned above. However, in some embodiments, thestabilization procedure can be synergistically performed in conjunctionwith another operative procedure in the same operative session, orwithin a month, 2 weeks, 1 week, 5, 4, 3, 2, or 1 days, or the same day;either before or after the spinal stabilization procedure, which can beanother minimally invasive spinal procedure in some embodiments. Forexample, one or more discectomies to remove a disc herniation can beperformed. In some embodiments, the procedure can also be performed inconjunction with a laminectomy done to decompress the spinal canal (forpatients with spinal stenosis), or in conjunction with posteriordistraction of the spinous processes to decrease in-folding of theligamentum flavum and to reduce the amount of neuroforaminal compromise(e.g., the X-STOP procedure from Medtronic, Inc., Minneapolis, Minn.).

The injection needle 50 can be withdrawn and one, two, or more flexiblerods 60, such as an approximately 2 mm in diameter carbon reinforcedPEEK curved rod would be placed through the anchor 30 with the distalend 62 of the rod 60 advanced into the cement 90 in the superiorvertebral body V2 before the cement has time to solidify, as shown inFIG. 2G. The injection needle 50 could be reintroduced into the proximaldilated end 34 of the anchor 30 in the inferior vertebral body V1 andanother volume of media, e.g., about 2-3 cc of PMMA can be injected toimbed the proximal end 64 of the rod 60 in cement 90 and into thecavity, extending into the surrounding bony trabeculae, as shown in FIG.2H. In some embodiments, the procedure can also advantageously benefitpatients who also have a vertebral body compression fracture byrestoring or improving the vertebral height of the fractured vertebrae.

The one, two, or more generally flexible carbon fiber rods 60, which canbe generally positioned along the cranial-caudal axis, span the discspace D and can limit translational movement but allow some limitedflexion and extension, in contrast to conventional spinal fusionswherein any relative movement of adjacent fused vertebrae may no longerbe possible. In some embodiments, multiple rods 60 can be placedside-by-side if additional stabilization is required. The PMMA cement 90immobilizes the proximal 64 and distal 62 ends of the one or more rods60 in the adjacent vertebral bodies V2, V1, but the cement 90 can beabsent in the central portion 36 of the anchor 30 (e.g., in theintervertebral disc space D; the cement 90 does not extend beyond thevertebral endplates into the disc space D in some embodiments), whichadvantageously preserves some degree of flexion and extension movementas noted above, such as about, at least about, or no more than about 1,2, 3, 4, 5, 6, 7, 8, 9, 10, or more degrees of flexion and/or extension,such as between about 1 degree and about 5 degrees, or between about 2degrees and about 5 degrees in some embodiments. The proximal 64 and/ordistal ends 62 of the rods 60 can extend some distance beyond theexpanded portions 32, 34 of the anchor 30 filled with bone cement 90 insome embodiments. The anchor 30 limits excessive extension andadvantageously prevents loosening, displacement, or other migration ofthe rod(s) 60. The rods 60 can advantageously further maintain theheight of the intervertebral disc space D and prevent the vertebrae V1,V2 from collapsing on each other. An embodiment of a system afterimplantation and removal of the curvable needle and cannula isillustrated in FIG. 21. In some embodiments, any number of the foregoingsteps can be repeated in order to effect multi-level spinal fusionsdepending on the desired clinical result.

Various other modifications, adaptations, and alternative designs are ofcourse possible in light of the above teachings. Therefore, it should beunderstood at this time that within the scope of the appended claims theinvention may be practiced otherwise than as specifically describedherein. It is contemplated that various combinations or subcombinationsof the specific features and aspects of the embodiments disclosed abovemay be made and still fall within one or more of the inventions.Further, the disclosure herein of any particular feature, aspect,method, property, characteristic, quality, attribute, element, or thelike in connection with an embodiment can be used in all otherembodiments set forth herein. Accordingly, it should be understood thatvarious features and aspects of the disclosed embodiments can becombined with or substituted for one another in order to form varyingmodes of the disclosed inventions. Thus, it is intended that the scopeof the present inventions herein disclosed should not be limited by theparticular disclosed embodiments described above. Moreover, while theinvention is susceptible to various modifications, and alternativeforms, specific examples thereof have been shown in the drawings and areherein described in detail. It should be understood, however, that theinvention is not to be limited to the particular forms or methodsdisclosed, but to the contrary, the invention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the various embodiments described and the appended claims.Any methods disclosed herein need not be performed in the order recited.The methods disclosed herein include certain actions taken by apractitioner; however, they can also include any third-party instructionof those actions, either expressly or by implication. For example,actions such as “accessing a vertebral body” includes “instructing theaccessing of a vertebral body.” The ranges disclosed herein alsoencompass any and all overlap, sub-ranges, and combinations thereof.Language such as “up to,” “at least,” “greater than,” “less than,”“between,” and the like includes the number recited. Numbers preceded bya term such as “approximately”, “about”, and “substantially” as usedherein include the recited numbers (e.g., about 10%=10%), and alsorepresent an amount close to the stated amount that still performs adesired function or achieves a desired result. For example, the terms“approximately”, “about”, and “substantially” may refer to an amountthat is within less than 10% of, within less than 5% of, within lessthan 1% of, within less than 0.1% of, and within less than 0.01% of thestated amount.

1. (canceled)
 2. A method for stabilizing the spine, comprising:creating a pedicular access channel in a pedicle to access the interiorof a first vertebral body; inserting an introducer cannula into thepedicle; inserting a hollow needle through a central lumen of theintroducer cannula into the interior of the first vertebral body,through an intervertebral disc, and into the interior of a secondvertebral body adjacent the first vertebral body; inserting an anchorhaving interstices through a lumen of the hollow needle such that adistal end of the anchor is within the interior of the second vertebralbody, a proximal end of the anchor is within the interior of the firstvertebral body, and a central portion of the anchor spans theintervertebral disc; expanding the distal end of the anchor within theinterior of the second vertebral body; expanding the proximal end of theanchor within the interior of the first vertebral body; flowing a firstvolume of media into the distal end of the anchor within the interior ofthe second vertebral body, wherein the media flows through theinterstices of the anchor outside the anchor and into the interior ofthe second vertebral body; flowing a second volume of media into theproximal end of the anchor within the interior of the first vertebralbody; and inserting a rod through the central lumen of the hollowneedle, such that a distal portion of the rod is positioned within theinterior of the second vertebral body and in contact with the firstvolume of media, the proximal portion of the rod is positioned withinthe interior of the first vertebral body, and a central portion of therod spans the intervertebral disc, wherein the rod resides at leastpartially within an interior of the anchor.
 3. The method of claim 2,wherein substantially no media flows within the intervertebral disc. 4.The method of claim 2, wherein the method does not involve a discectomyprocedure.
 5. The method of claim 2, wherein the media comprises PMMA.6. The method of claim 2, wherein the first volume of media is betweenabout 1 cc and about 5 cc.
 7. The method of claim 2, wherein the rodcomprises a carbon fiber material.
 8. The method of claim 7, wherein thecarbon fiber material comprises PEEK.
 9. The method of claim 2, whereinexpanding the distal end of the anchor within the interior of the secondvertebral body and expanding the proximal end of the anchor within theinterior of the first vertebral body comprises expanding a balloon. 10.The method of claim 2, wherein the inserting the anchor step comprisesinserting the anchor carried proximate the distal end of a ballooncatheter.
 11. The method of claim 2, wherein a central portion of theanchor is not expanded, and the distal and proximal expanded portions ofthe anchor have a maximal expanded diameter that is at least 2× theunexpanded diameter of the central portion of the anchor.
 12. The methodof claim 2, wherein the anchor comprises a shape memory material. 13.The method of claim 2, wherein the anchor is inserted in a compressedsubstantially tubular configuration.
 14. The method of claim 2, whereinfollowing insertion of the rod the first and second volumes of mediaharden, fixing the anchor and rod in place.
 15. The method of claim 2,wherein flowing the second volume occurs after the inserting a rod step,such that the proximal portion of the rod is in contact with the secondvolume of media after the flowing the second volume step.
 16. A systemfor stabilizing the spine, comprising: an anchor having a proximal end,a distal end, and a central portion, the anchor having a compressedtubular configuration and an expanded configuration wherein the proximalend and the distal end of the anchor are expanded while the centralportion of the anchor is not expanded, wherein the proximal end and thedistal end of the anchor have maximal expanded diameters at their widestportions of at least about 2× the diameter of the central portion of theanchor, wherein the anchor is sized and configured such that theproximal end of the anchor can reside within the interior of a firstvertebrae, the distal end of the anchor can reside within the interiorof a second vertebrae adjacent the first vertebrae, and the centralportion of the anchor spans an intervertebral disc between the firstvertebrae and the second vertebrae, wherein the anchor is defined by ashape memory frame and interstices within the frame along the axiallength of the anchor; a rod dimensioned to fit within an interior of theanchor, such that when implanted the rod is configured to residesubstantially within the anchor, wherein the distal end of the rod isconfigured to reside within the distal end of the anchor within theinterior of the second vertebrae, the proximal end of the rod isconfigured to reside within the proximal end of the anchor within theinterior of the first vertebrae and the central portion of the anchor isconfigured to span an intervertebral disc between the first vertebraeand the second vertebrae; and a volume of media, wherein the anchor isconfigured such that when the distal end of the anchor is inserted intothe interior of the second vertebrae and media is injected into thedistal end of the anchor, the media can flow through the interstices ofthe anchor outside the anchor and into the interior of the secondvertebrae.
 17. The system of claim 16, wherein the rod comprises PEEK.18. The system of claim 16, further comprising a balloon cathetercomprising a balloon configured to expand the proximal end and thedistal end of the anchor.
 19. The system of claim 16, wherein the anchoris carried on a distal end of the balloon catheter.
 20. The system ofclaim 16, wherein the media comprises PMMA.
 21. The system of claim 16,further comprising a curvable hollow needle comprising a central lumen.